you could make the whole sentence clearer.
"Modes de recharge

Méthode de calcul : pondération de l’utilisation de chaque type de recharge en fonction de la fréquence."
=
"Method of calculation: each method for recharging the battery was given a weighting proportional to its frequency of use"

"pondération" gives more than enough clues:
-- the sentence is about calculating the average length of the battery life;
-- there is at least two different modes / methods for recharging this battery, each leading to a different total "lifetime" of the battery i.e. one is preserving the longevity of the battery better than the other;
-- to calculate the estimated total lifespan of the battery, an average between the two "speed of ageing" is calculated, but not a simple average; that average is a "moyenne pondérée" (a "weighted average")
-- the "coefficient de pondération" / "weighting" given to each method of charging is (as one would expect) "en fonction de la fréquence." i.e. a recharging method used 70 % of the time will have a weighting of "70", all other methods together a weighting "30".